Transversely-excited film bulk acoustic resonators with electrodes having a second layer of variable width
There is disclosed acoustic resonators and filter devices. An acoustic resonator device includes a piezoelectric plate, and an interdigital transducer (IDT) formed on a front surface of the piezoelectric plate. The IDT includes interleaved fingers. At least one of the interleaved fingers includes a first layer adjacent the piezoelectric plate and a second layer over the first layer, wherein a width of the first layer is constant, and wherein a width of the second layer varies along a length of the at least one interleaved finger.
1. An acoustic resonator device comprising:
a piezoelectric plate; and
an interdigital transducer (IDT) at a surface of the piezoelectric plate, the IDT comprising interleaved fingers,
wherein at least one interleaved finger of the interleaved fingers comprises a first layer adjacent the piezoelectric plate and a second layer over the first layer,
wherein a width of the first layer is constant, and
wherein a width of the second layer varies along a length of the at least one interleaved finger.
2. The acoustic resonator device of claim 1 , wherein the piezoelectric plate and IDT are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the piezoelectric plate.
3. The acoustic resonator device of claim 1 , wherein a shape of the second layer of a first interleaved finger of the at least one interleaved finger is different from a shape of the second layer of a second interleaved finger of the at least one interleaved finger.
4. The acoustic resonator device of claim 1 , wherein the width of the second layer decreases linearly along at least a portion of a length of the second layer.
5. The acoustic resonator device of claim 1 , wherein a portion of the second layer is curved.
6. The acoustic resonator device of claim 1 , wherein the width of the second layer increases along a first portion of the second layer and decreases along a second portion of the second layer.
7. The acoustic resonator device of claim 1 , wherein a thickness of the first layer is less than a thickness of the second layer.
8. The acoustic resonator device of claim 1 , wherein the width of the second layer along a length of the at least one interleaved finger is less than or equal to the width of the first layer.
9. The acoustic resonator device of claim 1 , further comprising an adhesion layer between the first layer and the piezoelectric plate.
10. A filter device comprising:
at least one piezoelectric plate; and
a conductor pattern at a surface of the at least one piezoelectric plate, the conductor pattern including a plurality of interdigital transducers (IDTs) of a respective plurality of acoustic resonators, each of the plurality of IDTs comprising interleaved fingers,
wherein at least one interleaved finger of the interleaved fingers of at least one of the plurality of IDTs comprises a first layer adjacent the at least one piezoelectric plate and a second layer over the first layer,
wherein a width of the first layer is constant, and
wherein a width of the second layer varies along a length of the at least one interleaved finger.
11. The filter device of claim 10 , wherein the at least one piezoelectric plate and all of the plurality of IDTs are configured such that respective radio frequency signals applied to each IDT excites respective shear primary acoustic modes in the at least one piezoelectric plate.
12. The filter device of claim 10 , wherein a shape of the second layer of a first interleaved finger of the interleaved fingers of one of the plurality of IDTs is different from a shape of the second layer of a second interleaved finger of the interleaved fingers of the one of the plurality of IDTs.
13. The filter device of claim 10 , wherein the width of the second layer of at least one interleaved finger of at least one of the plurality of IDTs decreases linearly along at least a portion of a length of the second layer.
14. The filter device of claim 10 , wherein a portion of the second layer of the at least one interleaved finger of at least one of the plurality of IDTs is curved.
15. The filter device of claim 10 , wherein the width of the second layer of the at least one interleaved finger of at least one of the plurality of IDTs increases along a first portion of the second layer and decreases along a second portion of the second layer.
16. The filter device of claim 10 , wherein a thickness of the first layer of the at least one of the interleaved fingers of at least one of the plurality of IDTs is less than a thickness of the second layer.
17. The filter device of claim 10 , wherein the width of the second layer along a length of the at least one interleaved finger of at least one of the plurality of IDTs is less than or equal to the width of the first layer.
18. The filter device of claim 10 , further comprising an adhesion layer between the first layer of the at least one interleaved finger of at least one of the plurality of IDTs and the at least one piezoelectric plate.
19. The filter device of claim 10 , wherein the plurality of acoustic resonators comprises at least one first acoustic resonator and at least one second acoustic resonator, wherein a front side dielectric layer is deposited over the at least one first acoustic resonator and not deposited over the at least one second acoustic resonator.
20. A method of fabricating an acoustic resonator device, comprising:
forming an interdigital transducer (IDT) on a surface of a piezoelectric plate such that interleaved fingers of the IDT are disposed at the piezoelectric plate,
wherein at least one interleaved finger comprises a first layer adjacent the piezoelectric plate and a second layer over the first layer,
wherein a width of the first layer is constant, and
wherein a width of the second layer varies along a length of the at least one interleaved finger.
21. The method of claim 20 , wherein the piezoelectric plate and IDT are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the piezoelectric plate.
22. The method of claim 20 , wherein a shape of the second layer of a first interleaved finger of the at least one interleaved finger is different from a shape of the second layer of a second interleaved finger of the at least one interleaved finger.
23. The method of claim 20 , wherein the width of the second layer decreases linearly along at least a portion of a length of the second layer.
24. The method of claim 20 , wherein a portion of the second layer is curved.
25. The method of claim 20 , wherein the width of the second layer increases along a first portion of the second layer and decreases along a second portion of the second layer.
26. The method of claim 20 , wherein a thickness of the first layer is less than a thickness of the second layer.
27. The method of claim 20 , wherein the width of the second layer along a length of the at least one interleaved finger is less than or equal to the width of the first layer.
28. The method of claim 20 , further comprising forming an adhesion layer between the first layer and the piezoelectric plate.